1. Field of the Invention
The invention relates to a vacuum cleaning tool for a vacuum cleaning device comprising a housing in which a brush chamber and a turbine chamber are provided. A working roller, in particular, a brush roller, is arranged in the brush chamber transversely to the working direction of the vacuum cleaning tool. The working roller penetrates with a peripheral portion a suction slot provided in the bottom of the brush chamber. An air turbine is arranged in the turbine chamber for driving in rotation the working roller. A vacuum air flow of the vacuum cleaning tool enters the brush chamber via the suction slot, flows into the turbine chamber via an intake window provided in a partition between the brush chamber and the turbine chamber, and exits from the turbine chamber through an outlet window of a vacuum connector. In the flow direction of the vacuum airflow, the outlet window is positioned higher than the intake window. The turbine chamber has a chamber bottom and the chamber bottom has a ramp ascending toward the outlet window in the area where the vacuum airflow exits from the turbine chamber.
2. Description of the Related Art
In the housing of the vacuum cleaning tool according to U.S. Pat. No. 5,249,333, a brush chamber and a turbine chamber are formed. In the brush chamber a brush roller is arranged transversely to the working direction and penetrates to the exterior through a suction slot in the housing bottom of the brush chamber. For driving in rotation the brush roller, an air turbine is arranged in the turbine chamber which drives the brush roller by means of a belt drive. A vacuum airflow enters the brush chamber through the suction slot and flows into the turbine chamber through an intake window in the partition between the brush chamber and the turbine chamber. The vacuum air flow exits from the turbine chamber through an outlet window. The air turbine is formed as a so-called direct flow turbine, i.e., between two neighboring vanes a flow path is formed which opens into the center of the air turbine. The vacuum air flow therefore enters the vane-free center of the air turbine by flowing through the annular vane arrangement at one end and performs again work when exiting this center at the opposite end by flowing again through the annular vane arrangement.
This known configuration of a vacuum cleaning tool ensures a great output of the air turbine which, for strong vacuum air flows, is within the magnitude of an electric motor which can be used as an alternative for driving the brush roller.
It is an object of the present invention to further develop the vacuum cleaning tool of the aforementioned kind such that even for weaker vacuum air flows a strong turbine power output for driving the working roller is made available.
In accordance with the present invention, this is achieved in that the ramp provided on the turbine chamber bottom is trough-shaped with a groove extending in the flow direction of the vacuum airflow.
In the flow direction of the vacuum airflow the outlet window is positioned higher than the intake window so that the vacuum airflow is directed upwardly toward the outlet window. In this way, the vacuum airflow safely passes through the annular vane arrangement, enters the center of the turbine, and safely exits this center again. In the outflow area of the vacuum airflow the turbine chamber bottom is formed as a ramp and ascends to the outlet window wherein in the flow direction of the vacuum airflow the terminal edge of the ramp is positioned approximately at the level of the housing edge of the outlet window. In this way, the fault flow or secondary air which flows near the turbine chamber bottom is also guided in a directed way to the outlet window and can flow out without disruption. The deflected fault flow or secondary air therefore cannot impede the outflow of the vacuum airflow, which performs the work, so that indirectly the turbine power output is increased in this way.
The ramp is expediently trough-shaped with a groove extending in the flow direction of the vacuum airflow wherein the groove advantageously is matched in the area of the air turbine to the width of the air turbine and at the outlet side to the size of the outlet window. In this connection, the trough-shaped groove can be guided into the outlet window, in particular, can penetrate into it.
Preferably, the center of the outlet window is located as a point on the straight extension of the ramp surface which preferably symmetrically divides the outflow window at its center.
In a further embodiment of the invention a connecting line between the upper edge of the outflow window and the upper edge of the intake window is positioned below the hub of the air turbine. The circle segment of the air turbine cross-section which is separated by this connecting line has a surface area which is approximately 30% to 45% of the cross-sectional surface area of the air turbine.
When the annular vane arrangement has approximately 10 to 14 vanes and a connecting line is drawn between approximately the center of the intake window and approximately the center of the outlet window, this connecting line will intersect the air turbine as a secant. The circle segment which is separated by the secant has a circular arc which corresponds to the spacing of four to six, preferably five vanes, of the annular vane arrangement of the air turbine.